Created by: davidjb
This adjusts the load path for the configBridge.json file from one that's relative to where user is running the build or serve command (eg jekyll serve), to one that's relative to the source configuration setting for Jekyll.
The result is that a user can now have a _config.yml anywhere on her filesystem and point to Bootstrap's docs directory to use as Jekyll's source. Previously, customisations involved the original _config.yml needing to be modified inside (a forked) Bootstrap. Similarly, the jekyll command could only be run at the root of the Bootstrap package since the original file path to configBridge.json was only valid there; a command like jekyll serve --source path/to/bootstrap/docs (run from any directory) can succeed.
The existing behaviour is not affected as the grunt/ directory is always a sibling of docs in the current structure.